Conventionally, a toner used in electrophotographic image formation is filled in a toner container by a toner filling apparatus, and the toner container is set in an image forming apparatus. In a toner filling apparatus, as a toner transfer apparatus transferring a toner from a toner basket including a toner for filling to the toner container, an auger method rotating a spiral transfer member is known. However, in a toner transfer apparatus using an auger method, the toner receives a stress from friction with the rotating transfer member and possibly deteriorates in quality.
Japanese Patent No. 4335216 discloses a toner transferer feeding air to a toner in a toner basket to have higher fluidity and transferring the toner to a toner container by a reciprocating pump. The reciprocating pump includes a volume changing part changing its volume when a reciprocating member reciprocates. The reciprocating pump expands a volume of the volume changing part to introduce the toner from the toner basket and compresses the volume thereof to transfer the introduced toner to the toner container with pressure. Therefore, the reciprocating pump prevents a toner from deteriorating due to friction with the transfer member in the auger method.
However, a toner filling apparatus using a conventional reciprocating pump has a problem of large unevenness in amounts of toner filled in a toner container. This has the following reasons. The reciprocating pump does not quickly stop transferring toner when tuned off and transfers a small amount thereof. Therefore, the toner filling apparatus using the reciprocating pump includes a weigher weighing the toner container and stops the reciprocating pump when weighing a weight a little lighter than a weight of the toner container filled with a desired amount of toner.
A conventional reciprocating pump, when a period in which the completely compressed volume changing part is expanded and completely compressed again is one cycle, has the same time for expanding and compressing the volume of the volume changing part in one cycle of the reciprocation. The toner is fed to the toner container only when the volume changing part is compressed, and this is why a time for transferring the toner to the toner container is not longer than a half of the cycle. Thinking of a transfer amount of the toner per time more shortly divided from one cyclic time, when a time for transferring the toner to the toner container is not longer than a half of the cycle, a peak value of the transfer amount of the toner is larger than an average thereof during the cycle.
The conventional reciprocating pump has large unevenness of the amount of a toner fed after turned off according to timing of being turned off during the cycle. Specifically, when the pump is turned off just before the transfer amount of the toner has a peak value, the toner in an amount of the peak value is fed and comparatively a large amount of the toner is filled in the toner container. Meanwhile, when the pump is turned off while or just before expanding the volume of the volume changing part, almost no toner is fed after the pump is turned off. Thus, comparatively a large amount of the toner is filled in the toner container or almost no toner is fed after the pump is turned off, and amounts of the toner filled in the toner container have large unevenness after the filling process.
In order to prevent the unevenness of the amount of a toner filled in the toner container, a toner transferring apparatus using reciprocation and having a small difference between the peak value of the transfer amount of the toner and an average thereof during the cycle is required.
Further, when the peak value of the transfer amount of the toner is smaller than the average thereof during the cycle, stresses on the toner and each member forming the toner transferring apparatus can be decreased. The objects of preventing unevenness of filling amount in a filling apparatus and stresses on a fluid and each member forming a transferring apparatus are not limited to a toner transferring apparatus. Therefore, not only the toner transferring apparatus but also apparatuses transferring other fluids such as powders, liquids and gases besides a toner preferably have a small difference between a peak value of transfer amount and an average thereof during a cycle.
Because of these reasons, a need exists for a fluid transferer transferring a fluid using reciprocation and preventing an difference between an average of a transfer amount of the fluid and a peak value thereof during a cycle of the reciprocation.